S 2p photoexcitation spectra of SO2 at high resolution

The S 2p photoabsorption spectrum of gas-phase SO2 was studied at high resolution (Delta E congruent to 30 meV) using synchrotron radiation. The spectrum contains excitations to both valence orbitals and Rydberg states. The lowest core-to-valence excitation, S 2p(-1)3b(1), was found to be fivefold split, and vibrational subbands originating from the symmetric-stretching mode could be resolved. A Franck-Condon analysis of these five states reveals different geometries depending on the symmetry of the total electronic wave function in the final state. In the Rydberg region, both the spin-orbit splitting (congruent to 1.20 eV) and the ligand-field splitting (congruent to 95 meV) were resolved. (C) 1998 American Institute of Physics.